distanceTimeAnalysis: Visualizing the temporal evolution of flow variables

With the functions gathered in this module, flow variables of avalanche simulation results can be visualized in a distance versus time diagram, the so called thalweg-time diagram. The tt-diagram provides a way to identify main features of the temporal evolution of flow variables along the avalanche path. This is based on the ideas presented in [FFGS13] and [RKohler20], where avalanche simulation results have been transformed into the radar coordinate system to facilitate direct comparison, combined with the attempt to analyze simulation results in an avalanche path dependent coordinate system ([Fis13]). In addition to the tt-diagram, ana5Utils.distanceTimeAnalysis also offers the possibility to produce simulated range-time diagrams of the flow variables with respect to a radar field of view. With this, simulation results can be directly compared to radar measurements (for example moving-target-identification (MTI) images from [KohlerMS18]) in terms of front position and inferred approach velocity. The colorcoding of the simulated range-time diagrams show the average values of the chosen flow parameter (e.g. flow depth (FD), flow velocity (FV)) at specified range gates. This colorcoding is not directly comparable to the MTI intensity given in the range-time diagram from radar measurements.


The data processing for the tt-diagram and the range-time diagram can be done during run time of com1DFA, or as a postprocessing step. However, the second option requires first saving and then reading all the required time steps of the flow variable fields, which is much more computationally expensive compared to the first option.

To run

During run-time of com1DFA:

  • in your local copy of com1DFA/com1DFACfg.ini in [VISUALISATION] set createRangeTimeDiagram to True and choose if you want a TTdiagram by setting this flag to True or in the case of a simulated range-time diagram to False

  • in your local copy of ana5Utils/distanceTimeAnalysisCfg.ini you can adjust the default settings for the generation of the diagrams

  • run to calculate mtiInfo dictionary (saved as pickle in avalancheDir/Outputs/com1DFA/distanceTimeAnalysis/mtiInfo_simHash.p) that contains the required data for producing the tt-diagram or range-time diagram

  • run or and set the preProcessedData flag to True

As a postprocessing step:

  • first you need to run com1DFA to produce fields of the desired flow variable (e.g. FD, FV) of sufficient temporal resolution (every second), for this in your local copy of com1DFACfg.ini add e.g. FD to the resType and change the tSteps to 0:1

  • have a look at and

  • in your local copy of ana5Utils/distanceTimeAnalysisCfg.ini you can adjust the default settings for the generation of the diagrams

The resulting figures are saved to avalancheDirectory/Outputs/ana5Utils.


Fig. 25 Thalweg-time diagram example: The y-axis contains the distance from the beta point along the avalanche path (projected on the horizontal plane), e.g. the thalweg. Dots represent the avalanche front with the slope being the approach velocity. Red star marks the maximal approach velocity (this approach velocity is also projected on the horizontal plane).


The tt-diagram requires info on an avalanche path (see ana3AIMEC: Aimec). The simulated range-time diagram requires info on the coordinates of the radar location (x0, y0), a point in the direction of the field of view (x1, y1), the aperture angle and the width of the range gates. The maximum approach velocity is indicated in the distance-time diagrams with a red star and is computed as the ratio of the distance traveled by the front and the respective time needed for a time step difference of at least minVelTimeStep which is set to 2 seconds as default. The approach velocity is a projection on the horizontal plane since the distance traveled by the front is also measured in this same plane.


Thalweg-time diagram

First, the flow variable result field is transformed into a path-following coordinate system, of which the centerline is the avalanche path. For this step, functions from ana3AIMEC are used. The distance of the avalanche front to the start of runout area point is determined using a user defined threshold of the flow variable. The front positions defined with this method for all the time steps are shown as black dots in the tt-diagram. The mean values of the flow variable are computed at cross profiles along the avalanche path for each time step and included in the tt-diagram as colored field. When computing the mean values, all the area where the flow variable is bigger than zero is taken into account. For this analysis, all available flow variables can be chosen, but the interpretation of the tt-diagram structures and the corresponding meaning of avalanche front may be different for flow thickness or flow velocity.

Simulated Range-Time diagram

The radar’s field of view is determined using its location, a point in the direction of the field of view and the horizontal (azimuth) aperture angle of the antenna. The elevation or vertical aperture angle is not yet included. The line-of-sight distance of every grid point in the simulation results to the radar location is computed. The simulation results which lie outside the radar’s field of view are masked. The distance of the avalanche front with respect to the radar location is determined for a user defined threshold in the flow variable and the average values of the result field for each range gate along the radar’s line of sight are computed. This data is plotted in a range-time diagram, where the black dots indicate the avalanche front, and the colored field indicates the mean values of the flow variable for the range gates at each time step.